This invention relates to a tube apparatus for discharge of liquid from a container, in particular a separation tank, adapted to receive at least to different fluids with one or more intermediate boundary layers, where liquid outlet openings are located above and/or under the boundary layer(s).
A common use for such a liquid outlet is for draining at the bottom of a container. The tube apparatus according to the invention has primarily been developed for draining the water phase in an oil-water separator. However the apparatus is also well suited for use in two-phase separators with low liquid levels. As already indicated above there can in this connection generally be the question of more than two different liquids or fluid phases, since it can also be contemplated to employ the tube apparatus between two boundary layers in such a case with three or (more) different liquids, or the more interesting case of two liquids and a gas phase.
Conventional designs of outlet arrangements for liquid from containers and tanks are as a rule based on a single outlet at one point. This involves drawbacks related to strong local draining effects in the vicinity of the outlet opening. Thus entraining of liquid from surrounding portions of the container will very easily occur, so that outflow and mixing of different liquids or phases in the boundary layer will result. The invention aims at substantial improvements in this respect.
In practical cases of mounting of a tube apparatus according to the invention in a container, the outlet openings will normally be well elevated above the bottom of the container. A result of this is that entraining of particles and bottom deposits such as sand, from the region at the bottom will be prevented, which apparently is an advantage compared to an outlet opening located close to or flush with the bottom of the container.
The present invention comprises, in one embodiment, a tube apparatus for outlet of liquid from a container, adapted to receive at least two different fluids with intermediate interface(s), where liquid outlet openings are located above and/or under the interface(s). This tube apparatus comprises: (1) at least one tube member adapted to have a substantially horizontal position in the container and provided with at least two liquid outlet openings; and (2) a collecting tube that communicates with each tube member and serves to lead liquid out of the container, whereby immediately under and/or over each liquid outlet opening there is provided a substantially plate shaped flow control element which extends approximately horizontally in all directions in relation to the liquid outlet opening concerned.
The flow control elements of the tube apparatus have their largest extension out from the associated liquid outlet opening straight forward thereof. At least one of the flow control elements can be common to two or more of the liquid outlet openings. The collecting tube is adapted to stand approximately vertical in the mounted position in the container.
In one application, each tube member comprises: (1) a circular cross section; (2) liquid outlet openings formed as part of the circular cross section and delimited partially by an edge which is adapted to extend approximately horizontally; (3) and flow control elements generally flush with each limiting edge concerned.
In another application, each tube member comprises: (1) a rectangular cross section with corresponding full liquid outlet openings; and (2) flow control elements positioned flush with an upper and/or lower wall of each tube member.
The apparatus can be principally symmetrical about a vertical axis with all liquid outlet openings of equal dimensions. Further, the tube members residing in the horizontal plane are connected in an H-configuration by a transverse tube which connects a middle portion of two tube members to the collecting tube.
Alternatively, the apparatus can be asymmetrical about a vertical axis with all of the liquid outlet openings adjusted in size so that all of the liquid outlet openings will have approximately the same liquid flow volume.
Within the framework of the invention there may also be contemplated embodiments with two or more tube members each having only one liquid outlet opening, for example a configuration with three tube members extending each in its direction from a common collecting tube and having an associated liquid outlet opening at the outer free end of each tube member. By distributing a number of liquid outlet openings over a larger area, combined with associated flow control elements, adjacent boundary layers between different liquids or gases will be influenced to a negligible degree during operation. This invention seeks to implement this distribution of outlets with flow control elements to achieve the stated advantages.
The arrangement of one or more tube members and two or more liquid outlet openings can in central embodiments according to the invention, comprise tube members having each two liquid outlet openings. Within the framework of the invention, however, there may also be contemplated embodiments with two or more tube members each having only one liquid outlet opening, for example a configuration with three tube members extending each in its direction from a common collecting tube and having an associated liquid outlet opening at the outer free end of each tube member.
With a tube apparatus according to the invention mounted in a container or separator tank particularly good draining properties are obtained. By distributing a number of liquid outlet openings, for example 3, 4 or more openings, over larger area or portions of the container, combined with associated flow control elements, one (or two) adjacent boundary layers between two different liquids will be influenced to a negligible degree during operation. In the typical case of a boundary surface lying somewhat above the outlet openings, it is more specifically liquid flow directed downwards from the region at the boundary surface that is prevented. In actual practice this involves that for example in an oil-water separator the boundary surface or interface between oil and water can be positioned very close to the outlet openings without any risk of entraining of oil with the water during outflow. In a corresponding manner entraining of gas is prevented when a two-phase separator is concerned.